Robot mower displays E09 and returns to the charging station prematurely or will not leave the dock.

Safety first: Turn OFF the mower and disconnect it from the charging station before handling the battery. Do not short battery terminals.

• Check charge status: Leave the mower on the charging station until the display shows full charge. If E09 appears even after extended charging, suspect the battery.
• Inspect battery connections: Open the battery compartment and ensure the LawnMaster battery pack connector is fully seated and free of corrosion or burn marks.
• Look for swelling or damage: If the battery pack appears swollen, cracked, or smells burnt, discontinue use immediately and replace it.
• Measure voltage (advanced): With a multimeter, measure the pack voltage at rest. If it is significantly below the rated voltage after charging, the pack is failing.
• Reset system: Disconnect the battery for 5 minutes, then reconnect and attempt to start a short mow.

Persistent E09 usually indicates the battery pack has reached end of life. Replace with a genuine LawnMaster robot mower battery pack of the correct capacity and chemistry. If a new battery does not resolve the issue, the battery management circuitry on the main control board or in the pack may be faulty and require professional service.